The main issue with the development of a reliable constitutive model for explosive materials and concretes is the lack of a fundamental understanding of the evolution of 3-D microstructure and damage in these materials when they are subjected to multi-axial loading under confinement conditions. The main technical challenges are determining the 3-D microstructure and damage evolution processes and connecting the different length scales for damage and failure analyses. The programs basic approach involves a blend of numerical modeling and experimental studies. In Phase I, the 3-D microstructure and damage evolution processes as well as strain distributions will be determined using micro computed tomography techniques. 3-D numerical modeling analyses will be conducted to simulate damage initiation and evolution processes in a mock explosive material and concrete subjected to an incremental compressive load under a confinement condition. Constant compressive strain rate tests will be conducted on cylindrical specimens under a confinement condition. Acoustic emission techniques will be used to monitor damage processes. The data will be analyzed and the effect of strain rate on the strain distributions and damage process on the specimen surface are discussed.
Benefit: The research conducted here will provide the designer with a reliable method with which to evaluate the structural integrity and service life of penetrators thereby resulting in significant cost savings to the government and private companies as well as provide guidance for developing new high strength PBX materials. Furthermore, the techniques and methods developed to characterize PBX materials would also be applicable to characterizing other energetic materials, solid propellants, and concrete that would be of interest to the military and weapons industries as well as pressure and temperature sensitive materials that would be of interest to the oil and mining industries and shock absorbing materials that would be of interest to the transportation industries. In addition, the developed 3-D µ-CT imaging techniques can be used to take images and analyze the 3-D structure of bones, teeth, lungs, etc that would be of interest to the medical field.
Keywords: Explosive material, solid propellant, micro-computed tomography, acoustic emission, microstructure, cumulative damage, constitutive modeling
